This invention relates to fluid pumping systems, and more particularly to a beverage pumping system including a reciprocable pumping device having an improved valving system for ensuring dependable switching of the reciprocable member travel direction during operation, wherein the valving system is radially offset from the reciprocable member in order to obtain a more compact housing package.
Fluid pumping systems of the type disclosed in this application typically comprise a source of pumping fluid, such as beverage syrup in a soda fountain system or the like, and a pump. The pump typically includes a reciprocable member which reciprocates to pressurize the pumping fluid. A driving fluid under pressure, which may be either a liquid or a gas, is commonly used to reciprocate the reciprocable member. For example, the reciprocable member may be a piston having first and second faces which are alternately exposable to driving fluid under pressure and to exhaust.
A valve or valving system is provided for controlling the exposure of the piston faces to the pressurized driving fluid and to exhaust. In order for the valve system to perform its function, it typically includes one or more valve elements which must be moved periodically from one position to another to bring about reciprocation of the piston. The reciprocable member and the valving system are typically axially arranged in prior art systems, and movement of the reciprocable member can be used to control movement of the valve elements. In an axial arrangement of the reciprocable member and the valving system, the resulting pump package may be too bulky for certain applications. Therefore, what is needed for these applications is a way to differently configure the pump and valve arrangement so that it can be more compactly packaged.
Yet another element provided in prior art fluid pumping systems wherein the pump is reciprocatingly driven by a pressurized driving gas is a shut-off valve in the conduit between the source of driving gas and the pump. The shut-off valve ensures that should the supply of pumping fluid be interrupted, the supply of driving gas to the pump will be immediately interrupted as well, to prevent potentially damaging dry operation of the pumping system. Typical prior art valves are of the plunger valve type, and are designed to quickly close in response to the sudden drop in line pressure attendant to a cessation in the supply of pumping fluid. The problem is that the prior art valves, because of their design, are not always as stable as they should be. Occasionally, for example, when the pumping fluid supply is interrupted for a relatively long period of time, air may leak into the pumping fluid line. This air, which increases the line pressure above a vacuum level, may increase it sufficiently to cause the shut-off valve to open, thereby activating the pump under dry conditions and possibly damaging it.